The locking mechanism of a belt retractor that locks in emergency situations is usually activated mechanically. The vehicle-sensitive activation is normally effectuated by an inertia element that causes a pawl to engage with the ratchet of a disk cam which then stops, the relative rotation that then occurs between the belt spool and the disk cam being used to engage a locking pawl into position. With the belt-sensitive actuation, an inertia disk is used that can be rotated relative to the belt spool and that lags behind the rotation of the belt spool in cases of high acceleration of the belt, once again the relative rotation between the inertia disk and the belt spool being used to engage the locking pawl into position.
A short locking path is desirable in locking mechanisms for belt retractors. This can only be achieved with a relatively complicated,and intricate mechanism.